Dear Spinlanders
I thought I will give a few clarifications on this topic of the
'mystery liquid' during Helium fills, based on responses so far. I
realize that I put the cart before the horse in that, I didn't start
with a calibration/check of the testing equipment before I did this but
it was an on the spot urge to run to the lab and get the Fluke 714(B)
with its thermocouple for this experiment. But, I did to the follow up
on how well the temperature measurement went.
The thermocouple I used was Omega, K-type (chromel-alumel) and the
sensor temperature range is quite big : -270 C to +1372 C. The Fluke
714B thermocouple calibrator (sorry, I mentioned it as 'temperature
calibrator') is also up to the task, no problems. It goes from -200 C
all the way to +1372 C with a precision of 1.0 C in the temperature
range we are talking about.
I did not measure the temperature 'of the dripping liquid'. I was
only curious as to how cold the surface temperature of the stainless
steel parts of the manifold gets, when the dripping is observed. My
magnet helium manifold has a corrugated bellow type stretch, which
provided snug fit for the small fused joint of the thermocouple.
Now to the calibration of my measuring apparatus. I measured the
temperature of liquid Nitrogen with this combination and I got -190 C
i.e. 83 K. Giving allowance for the 'pedestrian' way I set up the
measurement i.e. not dipping only the tip of the junction but a large
length of the thermocouple wire in the LN2 path and other possible
errors, this measurement is not so far off from 77 K. Admittedly
making a leap of faith and extrapolating this Delta to the temperature I
measured, my 120 K should read as 114 K. This is still way off from the
boiling points of liquid Oxygen or liquid Nitrogen.
So, I am still wondering.....
Thank you
Rajan
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Rajan K Paranji, Ph.D.
NMR Facility Manager
Department of Chemistry
Room 65, Bagley Hall
University of Washington
Seattle, WA 98195
*ph: 206 685 2581
fax: 206 685 8665
email:paranji_at_chem.washington.edu <mailto:paranji_at_chem.washington.edu>
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Received on Thu Feb 19 2015 - 11:13:35 MST